18F-FLT Positron Emission Tomography and Magnetic Resonance Imaging of the Breast

It has been reported that PET (Positron Emission Tomography) scan is also useful in diagnosing breast cancer. 18F-fluorodeoxyglucose (18F-FDG), which based on glucose metabolism for the determination of malignancy, is the most popular PET tracer at present. However, 18F-FDG is not tumor specific. Benign inflammatory lesions may also demonstrate increase in 18F-FDG uptake. On the other hand, low grade malignancy may have low 18F-FDG concentration. Recently, 18F-3'-fluoro-3'-deoxy-L-thymidine (18F-FLT), a radiolabelled analog of thymidine, has been used in imaging cell proliferation and monitoring of treatment effects for breast cancer patients. 18F-FLT is believed to be more specific than 18F-FDG for breast cancer diagnosis and may provide the underlined physiological and molecular manifestations of breast lesions in addition to anatomical manifestations from mammography, ultrasound or MRI. Yet, its potential role in differentiation of ambiguous or suspicious lesions found on conventional imaging, such like mammography or ultrasound, has not been reported. We have had an ongoing preliminary study regarding breast lesion diagnosis using 18F-FLT PET, with an overall sensitivity 100% and specificity 92.7% in this dataset (from 2010 August to 2010 December, 19 lesions from 8 women with correlation with biopsy and clinical outcome). On the other hand, the molecular subtypes of breast cancer, including ER (Estrogen receptor), PR (Progesterone receptor), HER2 (Human epidermal growth factor receptor 2) are associated with treatment planning and prediction of clinical outcome of breast cancer. There have been documented reports regarding the relation of mammography, DCE MRI, 18F-FDG PET to ER, PR, HER2 status of breast cancers. But the association of proton MRS, DWI and 18F-FLT PET with ER, PR, HER2 status was seldom reported.